Fuse plug



April 2, 1935- H, RusKlN 1,996,258

FUSE PLUG Filed Jan. l2, 1934 2 Sheets-Sheet l nu o #d /l 1 1,2 o g.

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n April 2, '1935. H. RUSKIN 1,996,258

FUSE PLUG Filed Jan. 12, 1934 2 sheets-sheet 2 W97: ry )PaS/ta.

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z/EJT Patented Apr. 2, 1935 UNITED STATES PATENT OFFICE FUSE PLUG Henry Ruskin, Chicago, Ill.

Application January 12, 1934, Serial No. 706,317 9 claims. (ci. 20o-125)4 My invention relates to fuse plugs, particu- A, the top or cover element B, and the bottom larly to multiple fuse plugs in which a number element C. The body part A comprises a cyof fuse links are provided and arranged for selindrical annular wall I from whose upper part lective inclusion in a circuit to be protected, so extends a ilange structure comprising the horithat by the turning of a switch element'forming zontal portion II and the vertical or annular por- 5 part of the plug structure anfintact fuse link tion I2 which extends a distance above '-Lie upmay be substituted in the circuit for a fuse link per edge of the wall IIJ, the top of the horizonwhich has been blown. tal flange part Il being a distance below the up- An important object of the invention is to proper edge of the wall I0.

vide an arrangement in which each fuse linkage Substantially midway between its ends the wall 10 for connecting the plug terminals comprises a Ill has the cross wall or partition I3 and the walls main fuse element and a comparatively lighter I0, Il, I2 and I3 all form part of an integral or pilot fuse element, with the fuse elements conpreferably molded structure of suitable insulatnected in a parallel or shunt relationship and ing material.

with the fusion or explosion point of the main Depending from the partition wall I3 is the lug 15 fuse element confined within an explosion cham- I4 between which and the wall I0 extend radial ber and the fusion or explosion point of the light- `partition walls I5 which divide the space below er or pilot fuse element at some other location the wall I3 into explosion chambers I6, six such to be visible from the exterior of the plug so chambers being shown. The partition I3 and that the blown fuse linkages may be distinguished the upper end of the wall I0 dene a cylindrical 20 from the intact fuse linkages. terminal or contact chamber I1.

A further important object is to provide an The top or cover structure B comprises a cylinindividual explosion chamber for the main fuse drical body I8 tting into the flange part I2 to element of each fuse linkage and a correspondform a top closure for the contact chamber I1, the

ing individual visibility point for the pilot fuse depending ilange I9 of the cover body I8 extend- 25 element. ing down between the ilange part I2 and the wall Another important object is to provide im- I0 and seating against the top of the ange part proved arrangement for assuring adequate and II. An enlargement or boss 20 extends radially good electrical contact between the fuse linkage on the cover body I8 from the central part thereterminals and the plug terminals. of and overhangs and engages the top ot the 30 Still another object is to provide simple and flange part I2, this boss serving as a handle or substantial parts for the plug structure which finger grip whereby the cover structure B may may be readily assembled in `cooperating relabe rotated on the body part A. tionship for the consecutive or selective inclusion The bottom member C comprises the tapering of any of the fuse linkages in the circuit to be body 2I extended at the top to form a flange 22, 35 protected. the flange abutting the lower end of the wall I0 The above enumerated and other ieatures of so that the bottom part C forms a bottom closure the invention are incorporated in the structure for the explosion chambers I6. The member C disclosed 0n the drawings, in Which draWingS- has the cylindrical boss 23 on its top for engaging Figure lis a top View 0f my improved plug; in the recess 24 in the lug I4, such engagement 4o Figure 2 iS 8 Section 0n plane II--II 0f Fgcentering the part C on the part A of the plug 111'@ 1? structure.

Figure 3 is a top view of the plug with the upper or rotatable element removed; Figure 4 is a lower end view oi the plug body Extending axially through the bottom part C and through the wall I3 and its lug Il is a cylindrical pin or rivet 2li` which continues through 5 -wlgi mi gusi lnk'agsvl'erfl the 1u bottom the contact chamber I1 and through the openmemgtr. p p g ing 26 in the cover body I8 and into the enlarged Figure 6 is a side elevation of one of the fuse Opening 21 m the 'boss 2n At its lower end the linkages; f pin has the ilange or head 28 abutting the bot- 50 Figure 7 is top View of one of the fuse linktom of the part Cand at its upper end the pin is ages; and tubular and is deflected to form a ilange 29 for Figure 8 is a perspective view showing a modlabutting against the 150D 0f the Cover bOdY i S0 fled fuse arrangement. that the parts A, B and C are held together 56 The plug shown comprises the body element against axial displacement but permitting rotary 65 movement of the cover part B relative to the body part A.

' The cover or top part B has the cylindrical depending projection 30 tting and engaging in the terminal or contact chamber I'I and has a radially extending slot or pocket 32 for receiving the contact member S. The member shown is formed of a length of resilient metal band bent to S-shape with the inner end 33 bent to circular form to receive and intimately clamp the pin 25,

the outer end 34 of the spring extending tangentially for extended contact engagement with fuse elements. As the top or cover part B is rotated, the spring within the radial pocket 32 will follow such rotational movement for engagement of the spring end with the desired fuse structure. The partition wall I3 may have the annular bead 35 at its upper side surrounding the pin 25 to afford a bearing surface for the contact spring as it follows the movement of the cover part B.

The pin and contact spring form the movable terminal of the plug, the other terminal for the plug being the shell 36 having the threading 3l. The 'shell has the opening 38 in its base for receiving the lower part of the plug bottom member C and for abutting against the flange 22,

' the cylindrical body of the shell surrounding the lower end of the wall A.

As shown in Figures 1 to 4, each fuse structure F is a band of fuse material cut out to leave two fusion restrictions or necks 39 and 40, the neck 39 being wider and of greater cross-section and forming the main fusion point while the neck 40 is of much less cross-section and forming the pilot fusion point. Each fuse structure extends longitudinally around the wall ID and through one of the explosion chambers I6 with the main fusion point 39 within the explosion chamber and the pilot fusion point 40 extending across the top of the wall I0. There is sufficient clearance space between the body IB of the top member B and the top of the Wall I0 for the passage of the fuse bands and the part of the wall I0 surrounding the contact chamber II has channels 4I in its inner side for receiving the fuse bands, these channels communicating with passages 42 through the partition wall I3. In the lower edge of the wall I0 are the transverse channels or grooves 43 through which the fuse bands extend and the lower plug member C has lugs or projections 44 on its upper side engaging inthe channels 43 to hold and align the fuse structures and also to lock the part C against rotation relative to the part A. The flange part II on the wall A has the passageways 45 therethrough for the fuse bands, the flange I9 on the body I8 of the top part B being of suflicient greater diameter than the wall I0 to permit passage of the fuse bands. The fuse bands are applied to the body part A before application thereto of the top and bottom parts B, and C. The passages 42 are flared at their lower ends so that the fuse bands may be readily inserted upwardly through the passages and into the channels 4I. The upper ends of the fuse bands are then cleflected across the top of the wall A with the pilot fuse sections 40 extending thereacross, the fuse band ends then being deflected downwardly through the passages 45 and with their ends extending into the circumferential groove 46 in the wall A below the flange part I I.

The heavier fuse points 39 of the fuse bands will be located in the respective explosion chambers I6 and the lower ends of the bands are deected outwardlyl through the channels 43 and then upwardly along the outside of the wall I 0 and with the ends extended into the groove 46 overlapping the other ends of the bands.

After the fuse structures have thus been properly placed the top and bottom parts B and C are applied, the contact spring having first been slipped over the pin 25, and the pin is then riveted over at its upper end so that the plug structure parts are" locked together. The terminal shell 36 is then applied and its upper edge is deflected into the groove 46. and against the ends of the fuse bands to make electrical contact therewith.

When the plug is inserted in the terminal base for inclusion in the circuit to'be protected, the current flow between the terminal shell and the contact spring will be in two parallel or shunt paths through the fuse structure with which the contact spring engages, one path from the terminal shell to the Contact spring being through the lower part of the fuse band which has the main fusion point or section 39, and the other path being through the upper part of the fuse band which has the pilot fusion point or section 40. The resistance of the fusion point determines the proportionate current flow therethrough, the resistance at the fusion point 40 being preferably such that there would be very little current ow therethrough but with the greater part of the current low through the main fusion point 39. Upon excess current flow the fuse structure will blow simultaneously at both fusion points. There will be very littlearcing or gassing at the pilot fusion point 40 and practically all of the explosion, arcing and gassing will take place in* the conned explosion chamber I6 through which the blown fuse extends.

The pilot fusion point 40 is visible, the top part B having a sight opening 4'I in line with the top of the wall A over which these pilot fusion points of the fuse structures extend. As a matter of protection and precaution, a transparent member such as a mica plate 48 is interposed between the cover part B and the wall- I0, the mica pane shown being annular and surrounding the cylindrical lug 30 on the top member B, the mica pane being preferably perforated to receive projections or lugs 49 on top of the wall I0 so as to be held in proper position. After blowing of one of the fuse structures, the plug top B is rotated to swing the contact spring into engagement with an intact fuse structure and the sight opening 41 will then be in alignment with the pilot point 40 of such fuse structure. If this pilot fuse point or section is unbroken then it indicates that the entire fuse structure is intact and ready for service.

It will be noted that the lower end of the wall I0 is tapered slightly on its outside so that the shell 36 may be readily applied. The shell was primarily of an internal diameter equal substantially to the outer diameter of the cylindrical part of the wall I0 above its tapered end so that when the shell is forced along the fuse bands extending along the outside of the wall I 0 the shell will be slightly expanded and tensed so that it will exert clamping pressure against the fuse bands and make intimate contact therewith along an extended area, and, when the rim of the ange is deflected into the groove 46, the shell will be locked in place and the overlapping ends of the fuse bands will be clamped to the body A and held in electrical engagement. Should the terminal shell become heated while the plug is in service any resulting expansion thereof would not be sufficient to loosen the shell and destroy its clamping action on the body A and against the fuse structures.

As shown on Figures l and 3 the ange part I2 may have on its top indications 50 which may be depressions as shown and which are located and spaced to accord with and indicate the proper position of the switch spring relative to the respective fuse structure.

Figure 8 shows a modified arrangement of fuse structure. It may be that it will be desirable to use fuse material in the form oi wire instead of in the form of sheets or bands, particularly for the pilot fusion part of the fuse structure. In the arrangement shown in Figure 8, channels or recesses 5I are provided in the inner side oi' the contact chamber I1 and each receives the coiled or folded end 52 of a length of wire fusing material, the outer end of the wire extending around the top of the wall I0 and then downwardly for engagement with the terminal shell 3G. The heavier fuse element 53 may also be of wire, or as shown, may be in the form of a. fuse band with the fusion neck 54 within the explosion chamber I6. The outer end of this fuse member will overlap the end oi the wire fuse and be clamped in the groove 46 by the terminal shell. The inner end of the fuse band would extend upwardly through the passageway l2 into the contact chamber I1 and overlap the coiled end 52 of the wire fuse. This coiled end would have ample electrical engagement with the end of the fuse band and the ends of both fuse members would then be in elec- 'trical engagement with the contact spring as the spring is brought into engagement with the fuse bands. In order to assure blowing of the wire fuse at a point where it crosses the top of the wall I0 and be visible through the mica pane and sight opening 41, the fuse at that point will be made of reduced cross-section as for example by being dented as indicated at 55. 1

The passageways I2 from the explosion-chambers to the contact chamber are of such dimension that the fuse material extending therethrough will seal the passageways against the escape of flame or gas from the explosion chamber to the contact chamber when the fuse blows. The blowing at the pilot fusion point 40 will not cause any material ame or gas so that the fuses can be carefully observed through the mica pane even at the instant when the fuse is blown.

I have shown practical and eilicient embodiments of the features of my invention, but I do not desire to be limited to the exact construction, arrangement and operation shown and described, as changes and modications may be made without departing from the scope of the invention.

I claim as follows:

1. A fuse plug comprising a housing providing an explosion chamber and a terminal chamber separated by a partition, a. passageway through said partition connecting said chambers, a terminal in said terminal chamber, a terminal on the outside of said housing, a fuse link extending from said outside terminal and through said explosion chamber and said partition passageway into said terminal chamber, said fuse link having a fusion part of low resistance located in said explosion chamber, a light fuse link extending from said outside terminal and into said terminal chamber, the ends of said fuse links in said terminal chamber being vadapted for engagement by said terminal in said chamber whereby said fuse links will be connected in parallel between said terminals, said light fuse link having a fusion part visible from the exterior of said plug.

2. In a fuse plug, the combination -oi a housing providing a plurality o! explosion chambers and a contact chamber, a partition between said explosion chambers and said contact chamber having passageways between said explosion chambers and said contact chamber, a stationary terminal for said plug on the outside of said housing, a movable terminal for said plug within said terminal chamber, fuse linkages between said terminals each comprising a comparatively heavy fuse link extending from said external terminal into one of said explosion chambers and through the corresponding passageway in said partition into said contact chamber and a comparatively light fuse link extending from said external terminal into said contact chamber, means for moving said internal contact for selective engagement with the corresponding ends oi said fuse linkages whereby the heavy and light links of said linkages will be connected in parallel in the circuit with which the plug may be associated, said heavier fuse links having weakened fusion sections located within the respective explosion chambers, and said lighter fuse links having weakened fusion sections visible from the exterior of the plug.

3. In a fuse plug, a housing comprising an annular wall having a cross partition providing a contact chamber above the partition, walls forming explosion chambers below said partition, said partition wall having passageways connecting said explosion chambers with said contact chamber, fuse linkages extending around said annular wall, each fuse linkage extending through said contact chamber and through one of said partition passageways and one of said explosion chambers, an external plug terminal engaging with the outsides of said fuse linkages, a contact movable in said contact chamber for selective engagement' with the inner sides of said linkages whereby said linkages will be connected in parallel between said external terminal and said contact, each linkage having a fusion part of comparatively low resistance located in the respective explosion chamber and having a fusion part of comparatively high resistance outside of the explosion chamber and the contact chamber and visible from the exterior of the plug.

4. In a fuse plug, the combination of a housing comprising an annular wall having a cross partition forming an explosion chamber below the partition and a contact chamber above the partition, said partition having passageways connecting the explosion chamber with the contact chamber, a contact terminal on the outer side of said housing, a movable contact terminal in said contact chamber, and a plurality of fuse linkages, each fuse linkage comprising a light fuse link extending from said outer terminal contact and around the top of said annular wall into said contact chamber and a heavier fuse linkage extending from the outer contact terminal around the lower end of said annular wall and through said explosion chamber and one of said partition passageways and into said contact chamber whereby each linkage structure when engaged by the movable terminal contact will have its links included in parallel between the outer terminal contact and said movable contact, each heavier link having a fusion part located within said explosion chamber, and each lighter link having a fusion part where it extends around the top of said annular wall, and means cooperating with said movable contact i'or making visible the fusion part o! the light links.

nular wall having a cross partition dividing said housing into a contact chamber and an explosion chamber, said partition wall having a passageway connecting said chambers, a. fuse linkage extending around said annular wall and through said partition passageway and said chambers, an external plug terminal engaging with the outside of said fuse linkage, an inner plug terminal engaging said linkage in said contact chamber, said linkage having a fusion part of comparatively low resistance located in the explosion chamber and having a fusion part of comparatively high resistance between said inner plug terminal and the outer plug terminal and visible from the exterior of the plug.

6. In a fuse plug, inner and outer plug terminals, a fuse link connected at its ends with the said inner terminal, means forming an inclosure for said low resistance fusion part, and means making said high resistance fusion part visible from the exterior of the plug.

7. A fuse plug having circuit contact terminals, a single fuse strip contacting at its ends with one of said terminals and at an intermediate point with said other terminal whereby to interpose two parallel fuse sections between said terminals, one of said sections having a comparatively low resistance fusion portion and the other section having a comparatively high resistance fusion portion, means conilning said low resistance fusion portion within said plug, and means rendering said high resistance fusion portion visible from the exterior of the plug.

8. In a fuse plug, an annular body providing a contact chamber in its upper part, a plurality of fuse linkages each comprising a link of comparatively low fusion resistance extending from said contact chamber around the lower edge of said annular body and to the exteriors thereof and a pilot fuse link of comparatively high fuse resistance extending from said contact chamber around the upper edge of said annular body and to the exterior thereof, an outer terminal for said plug surrounding said body and contacting the outer ends of the links of the fuse linkages, a cover rotatable on said body,- an inner terminal for said plug and a contact arm engaging therewith and rotatable with said cover for selective engagement with said fuse linkages, said cover having a sight opening register with the upper edge of said body whereby said pilot fuse links may be visible from the exterior of the plug.

9. In a fuse plug, the combination of a body having partition walls providing a contact chamber in the upper part thereof and a plurality of explosion chambers in the lower part thereof, fuse linkages each comprising a mainfuse section extending from the contact chamberV through one of said explosion chambers and around the lower edge of said body to the exterior thereof and a pilot fuse section extending from the contact chamber around the upper edge of said body to the exterior thereof, a bottom member engaging the lower end of said body to close said explosion chambers, a cover part rotatably mounted on said body, an outer terminal for the plug surrounding said bottom part and the lower end of the body part and 'contacting with theputer ends of the fuse sections of said fuse linkages, an inner terminal for said plug extending through said body and said bottom part and cover part and serving to hold said parts axially together, and a contact arm in said contact chamber connected with said inner terminal and movable with said cover part for selective engagement with said fuse linkages, said cover part having a sight opening through which the pilot fuse links of said fuse linkages are visible from the exterior of the plug.

HENRY RUSKIN. 

